KB5066875 is the ESU Monthly Rollup Update for Windows Server 2012. It was released on 14 October 2025 under the ‘Patch Tuesday’ program.
Salient points
- KB5066875 supersedes KB5065509 released in September 2025.
- KB5066875 requires the KB5066795 Servicing Stack Update to be installed prior to installing the main monthly rollup update.
- Without the installation of KB5066795, the ESU KB5066875 cannot be installed. For WSUS administrators, KB5066795 needs to be approved before KB5066875 will be fetched and deployed automatically.
- If you install language pack after installing KB5066875, you would need to reinstall the security update. All language pack installations must be completed before installing the monthly rollup update on Windows Server 2012.
- KB5066875 is an Extended Security Update. A valid subscription key to the ESU program is required before installing the monthly rollup update.
- Windows Server 2012 is impacted by 41 security vulnerabilities reported in October 2025 security bulletin.
- Two of these vulnerabilities have CRITICAL severity.
- Two zero-day vulnerabilities affect Windows Server 2012 and Windows Server 2012 Server Core installation in October security bulletin released alongside the Windows Updates on 14 October 2025.
Servicing Stack Update KB5066795
The Servicing Stack Update for Windows Server 2012 for October 2025 is KB5066795. It corresponds to KB5066875 ESU.
For automated deployments of KB5066875 through the Windows Update program, the Servicing Stack Update KB5066795 is offered for installation as part of the installation process of the monthly rollup update KB5066875.
The Servicing Stack Update file is a small file little under 10 MB. Upon installation, it would not cause server reboot.
Once the SSU is installed, you can proceed with the installation of the main monthly rollup update KB5066875.
Download KB5066875
You can download the monthly rollup update KB5066875 for Windows Server 2012 from the Windows Update Catalog page shared below:
We would reiterate that you need a valid ESU program subscription before you could install the ESU KB5066875 on Windows Server 2012.
Zero-day Vulnerabilities
Three zero-day security vulnerability affects Windows Server 2012 and Windows Server 2012 Server Core installation.
| Vulnerability | CVSS Score | Severity | Description |
|---|---|---|---|
| CVE-2025-24990 | 7.8 | Important | Elevation of Privileges affecting Windows Agere Modem Driver |
| CVE-2025-47827 | 4.6 | Important | Secure Boot bypass in IGEL OS before 11 |
| CVE-2025-59230 | 7.8 | Important | Elevation of Privileges vulnerabity in remote access connection manager |
Critical vulnerabilities
There are 51 reported security vulnerabilities in Windows Server 2012 for October 2025. The 2 CRITICAL vulnerabilities affecting Windows Server 2012 are shared below.
| Vulnerability | CVSS | Description |
|---|---|---|
| CVE-2025-59287 | 9.8 | Windows Server Update Service (WSUS) Remote Code Execution Vulnerability |
| CVE-2016-9535 | 4.0 | LibTIFF Heap Buffer Overflow Vulnerability |
Internet Explorer Cumulative Update – KB5066840
To secure the Windows Server 2012, you also need to patch Internet Explorer 11 with the latest cumulative update. KB5066840 is the cumulative update for Internet Explorer released on 14 October 2025.
You can download the IE Cumulative Update for Windows Server 2012 from the link shared below:
Download Cumulative Update for Internet Explorer – KB5066840 (54.9 MB)
KB5066875 – Changelog
Since this is an ESU, the focus remains on securing the Windows Server 2012 deployments. The following changes have been reported for KB5066875:
- [Internal Windows OS] Miscellaneous security improvements were made to internal Windows OS functionality.
- [Stability issue] Fixed: This update addresses an issue observed in rare cases after installing the May 2025 security update and subsequent updates causing devices to experience stability issues. Some devices became unresponsive and stopped responding in specific scenarios.
- [Fax modem driver] This update removes the ltmdm64.sys driver. Fax modem hardware dependent on this specific driver will no longer work in Windows.
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